AB0646 CONCORDANCE OF THE DIAGNOSIS AND CLASSIFICATION OF SYSTEMIC LUPUS ERYTHEMATOSUS
Authors: C. Popescu, A. Minzararu, M. Agache, C. E. Ionescu, C. Codreanu
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Systemic lupus erythematosus (SLE) is a chronic, multisystemic autoimmune disease of unknown etiology. A defining characteristic is its immunological anomalies such as the production of antinuclear antibodies (ANA). Polymorphic clinical manifestations, the absence of pathognomonic signs and the absence of specific laboratory tests for SLE, make the diagnosis difficult. Although they have been developed for the homogenization of patients included in clinical trials, the SLE 2019 EULAR (European Alliance of Associations for Rheumatology)/ACR (American College of Rheumatology) classification criteria [1] can serve as a guide or diagnostic verification in individual cases from current medical practice. <h3>Objectives</h3> The study assessed the characteristics and consistency of the diagnosis and classification of SLE in order to measure a potential patient pool for inclusion in clinical trials. <h3>Methods</h3> The study retrospectively evaluated the conformity of the 2019 EULAR/ACR classification criteria in patients discharged from a single-center tertiary university rheumatology center between February 2020 and February 2022, diagnosed with SLE according to their attending rheumatologists and identified by international classification of diseases (ICD10) codes. Normally-distributed continuous variables are reported as “mean ± standard deviation”. The correlation of continuous variables was studied with Spearman tests. Differences of continuous variables between nominal dichotomous subgroups were evaluated with Mann Whitney tests. Statistics were considered significant if p &lt; 0.05. <h3>Results</h3> The study included 146 patients, of whom 92.5% were women, with an average age of 48.3 ± 13.3 years. Approximatively 7.5% of patients had negative ANA (including at repeated measurements) and 12.3% had an unknown ANA status. The method for determining ANA was ELISA (enzyme-linked immunosorbent assay; 75.3%), indirect immuno-fluorescence (2.7%) or undetermined (21.9%). Men scored a significantly higher median number of classification points than women (i.e., 21 points versus 16 points; p = 0.020) and they had a higher prevalence of class 3/4 nephritis (18.2% versus 3.0%; p = 0.014), pleuritis/pericarditis (36.4% versus 14.8%; p = 0.064) and oral ulcers (27.3% versus 9.6%; p = 0.072). Only 63.7% of SLE diagnoses also met the 2019 EULAR/ACR classification criteria. The most common manifestations not complying with these classification criteria were proteinuria (59.5% discordance), thrombocytopenia (13.6% discordance) and joint involvement (9.3% discordance). The median number of classification points correlated significantly with the median titer of ANA (<i>rho</i> = 0.301; p = 0.001) measured by ELISA. <h3>Conclusion</h3> Diagnostic reality includes ANA-negative SLE, which should be further investigated. In clinical practice, ANA are preferably determined by ELISA and their titer seems to be proportionally associated with more classifiable SLE clinical characteristics. Clinical trials have a maximum eligible SLE population of 63.7% of patients to whom additional inclusion/exclusion criteria could be applied. <h3>Reference</h3> [1]Aringer <i>et al</i>. Arthritis Rheumatol. 2019; 71 (9), 1400-1412. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.